Drug resistant Gram-negative bacteria are a major cause of mortality and morbidity in the world and new strategies for treating them are greatly needed. The objective of this proposal is to develop a new strategy for targeting ciprofloxacin into drug-resistant Gram-negative bacteria, composed of conjugating maltohexaose to antibiotics. Maltohexaose-conjugated antibiotics are designed to be selectively imported by bacteria via the maltodextrin (MD) transporter, but should be minimally internalized by mammalian cells due to their lack of MD transporters. After internalization, maltohexaose conjugated antibiotics are designed to be cleaved and release the free antibiotic within the bacterial cytoplasm. The central hypothesis of this proposal is that conjugates of maltohexaose with ciprofloxacin, termed MDC-1 and MDC-2, will be transported into drug-resistant P. aeruginosa by a factor of 10 greater than free ciprofloxacin, and will have increased antibiotic potency relative to that of free ciprofloxacin. In addition, we hypothesize that MDC-1 and MDC-2 will have a wider therapeutic window than free ciprofloxacin at treating drug resistant P. aeruginosa in a lung infection model. The overall objective of this proposal will be accomplished by testing our central hypothesis through the following Specific Aims: R21, Phase Specific Aim 1. Synthesis and intracellular transport of MDC-1 and MDC-2. Specific Aim 2. Antibacterial activity of MDC-1 and MDC-2 against drug resistant P. aeruginosa. The completion of the R21 phase experiments will demonstrate that the therapeutic efficacy of ciprofloxacin can be improved by conjugating it to maltodextrins. These studies will serve as the foundation for the subsequent R33 phase, which focuses on investigating the in vivo therapeutic efficacy and generality of MDC-1 and MDC-2 in fighting bacterial infections. R33 Phase, Specific Aim 1. Determine the in vivo efficacy of MDC-1 and MDC-2. Specific Aim 2. Determine the efficacy of MDC-1 and MDC-2 against Gram-negative bacteria. The experiments in this proposal are innovative because they will for the first time develop a small molecule strategy for targeting drugs to bacteria, and represent the first attempt to exploit the maltodextrin transport pathway for drug delivery. The proposed project is significant because it has the potential to generate a universal platform for enhancing the delivery of structurally diverse antibiotics into multidrug resistant bacteria. This new approach therefore has the potential to significantly impact medicine, public health and national security by reducing the emergence of antimicrobial-resistant organisms and stimulating the development of novel antibiotics.